There is an ever increasing demand for power conversion and regulation circuitry to operate with increased efficiency and reduced power to accommodate the continuous reduction in size of electronic portable devices. Many times these devices are battery powered, and it is desirable to utilize as little power as possible to operate these devices so that the battery life is extended. Switching regulators have been implemented as an efficient mechanism for providing a regulated output in power supplies. One such type of regulator is known as a switching regulator or switching power supply, which controls the flow of power to a load by controlling the on and off duty-cycle of one or more switches coupled to the load. Many different classes of switching regulators exist today.
One type of power regulator is a buck-boost regulator, in which the output voltage is inverted relative to the input voltage. In a typical buck-boost regulator, a switch is used to periodically couple a positive rail voltage to a switching node that is separated from the output voltage by a diode. An inductor is configured to maintain a current flow that is drawn away from the switching node. In an on-state, the inductor current increases, and an output capacitor supplies power to the load. In an off-state, the inductor current decreases as the energy stored in the inductor discharges to provide power to the output capacitor and the load.
A typical power regulator can operate in one of two modes, which can typically depend on the size of the load of the power regulator. One mode is known as a continuous mode of operation. In a continuous mode, the power regulator rapidly switches between the on-state and the off-state (i.e., has a high-frequency duty-cycle), such that the current through the inductor is never fully discharged (i.e., equal to zero). While the continuous mode can be a substantially efficient mode of operation, it can be limited with regard to response time, such as in response to activation, deactivation, and/or load changes.
Another mode is known as a discontinuous mode of operation. In a discontinuous mode, the power regulator may have a substantially longer on-state and off-state. As a result, the current flow through the inductor can be substantially completely discharged at each cycle of the power regulator. The discontinuous mode therefore provides a greater response time with regard to the current through the inductor. However, operating in the discontinuous mode can be significantly less efficient, as the peak current through the inductor can be significantly greater than operation in the continuous mode.